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Table 40— Heating Service Analysis
PROBLEM CAUSE REMEDY
Burners Will Not
I
i
t
Misaligned spark electrodes. Check flame ignition and sensorelectrode positioning. Adjust as needed.
B
u
r
n
e
r
s
W
i
l
l
N
o
t
Ignite.
Nogasat main burners. Check gas line
f
or airpurgeas necessary.
A
fter purging gas line o
f
air, allow gas
g
N
o
g
a
s
a
t
m
a
i
n
b
u
r
n
e
r
s
.
C
h
e
c
k
g
a
s
l
i
n
e
f
o
r
a
i
r
p
u
r
g
e
a
s
n
e
c
e
s
s
a
r
y
.
A
f
t
e
r
p
u
r
g
i
n
g
g
a
s
l
i
n
e
o
f
a
i
r
,
a
l
l
o
w
g
a
s
to dissipate for at least 5minutes beforeattemptingto relight unit.
Check gasvalve.
Water in gas line. Drain water andinstall dripleg to trapwater.
Nopowerto furnace. Check power supply, fuses, wiring, and circuit breaker.
No 24 vpower supply to control circuit. Check transformer.Transformers withinternalovercurrent protection require a
cool-down periodbefore resetting. Check24-v circuit breaker;reset if neces-
sary.
Miswired orloose connections. Check all wiringandw irenut connections.
Burned-out heatanticipator inthermostat. Replace thermostat.
Broken thermostat wires. Run continuity check.Replacewires,if necessary.
Inadequate Heating. Dirty air filter. Clean orreplace filteras necessary.
I
n
a
d
e
q
u
a
t
e
H
e
a
t
i
n
g
.
Gasinput tounit too low. Check gaspressure at manifold.Clock gas meter for input.If too low, increase
manifold pressure orreplacewith correct orifices.
Unit undersizedfor application. Replace with proper unit or add additional unit.
Restricted airflow . Clean filter, replacefilter,or remove anyrestrictions.
Blower speedtoo low. Use high speed tap,increase fan speed, orinstall optional blower, as suitable
forindividual units,Adjust pulley.
Limitswitchcyclesmainburners. Check rotation of blower,thermostat heatanticipator settings,and temperature
rise ofun i t. Adjust asneeded.
Toomuch outdoorair. Adjust minimum position.
T
o
o
m
u
c
h
o
u
t
d
o
o
r
a
i
r
.
Check economizer operation.
Poor Flame
Characteristics.
Incomplete combustion (lack of
combustion air) results in:
Check all screws around flue outlets and burner compartment. Tighten as nec-
essary.
C
h
a
r
a
c
t
e
r
i
s
t
i
c
s
.
c
o
m
b
u
s
t
i
o
n
a
i
r
)
r
e
s
u
l
t
s
i
n
:
Aldehyde odors, CO (carbon monoxide),
t
i
f
l
f
l
t
i
f
l
Cracked heat exchanger.
A
l
d
e
h
y
d
e
o
d
o
r
s
,
C
O
(
c
a
r
b
o
n
m
o
n
o
x
i
d
e
)
,
sooting flame,or floating flame.
Overfiredunit — reduceinput,changeorifices,or adjust gasline ormanifold
pressure.
Check vent for restriction. Clean asnecessary.
Check orifice to burner alignment.
Burners Will Not
Turn Off.
Unit is locked into Heatingmode for a
one minute minimum.
Wait until mandatory one-minute time periodhas elapsedor reset powerto
unit.
Table 41—Perfect Humidity Adaptive Dehumidification System Subcooling Mode Service Analysis
PROBLEM CAUSE REMEDY
Subcooling Mode (Liquid Reheat)
Will Not Energize.
No power to control transformer from
evaporator-fan motor.
Check powersource and evaporator-fan relay.Ensure all
wireconnectionsaretight.
W
i
l
l
N
o
t
E
n
e
r
g
i
z
e
.
No power from control transformer to liquid line
solenoid valve.
1. Fuseopen;checkfuse. Ensure continuity of wiring.
2. Low-pressure switch open. Cycle unit off and allow
low-pressure switch to reset. Replace switch if it will
not close.
3.Transformer bad;check transformer.
Liquid line solenoid valve will not operate. 1. Solenoid coil defective;replace.
2. Solenoid valvestuck open; replace.
Liquid line solenoid valve will not open. Valve is stuck closed; replace valve.
Low System Capacity . Low refrigerant charge or frostedevaporatorcoil. 1. Checkcharge amount.Charge perFig.55---58.
2. Ev aporator coil frosted; checka nd replace low-pres-
sure switch if necessary.
Loss of Compressor Superheat
Conditions with Subcooling/Reheat
Dehumidification Coil Energized.
Thermostatic expansion valve (TXV). 1. CheckTXV bulb mounting,andsecure tightly tosuc-
tion line.
2. Replace TXV if stuck open or closed.
Table 42—Perfect Humidity Adaptive Dehumidification System Hot Gas Reheat Mode Service Analysis
PROBLEM CAUSE REMEDY
Reheat Mode Will Not Energize. No power to control transformer from
evaporator-fan motor.
Check powersource and evaporator-fan relay.Ensure all
wireconnectionsaretight.
No power from control transformer to hot gas
line solenoidva lve
1. Fuseopen;checkfuse. Ensure continuity of wiring.
2. Low-pressure switch open. Cycle unit off and allow
low-pressure switch to reset. Replace switch if it will
not close.
3.Transformer bad;check transformer.
Hot gas line solenoidvalve will not operate. 1. Solenoid coil defective; replace.
2. Solenoid valvestuck closed;replace.
Low refrigerant charge or frosted evaporator coil. 1. Check charge amount.Charge perFig.55---58.
2. Ev aporator coil frosted; checka nd replace low-pres-
sure switch if necessary.
Loss of Compressor Superheat
Conditions with Subcooling/Reheat
Dehumidification Coil Energized.
Thermostatic expansion valve (TXV). 1. CheckTXV bulb mounting,andsecure tightly tosuc-
tion line.
2. Replace TXV if stuck open or closed.
Excessive Superheat. Liquid line solenoidvalve will not operate. Valve isstuck, replace valve.
E
x
c
e
s
s
i
v
e
S
u
p
e
r
h
e
a
t
.
Hot gas line solenoidvalve will not close. Valve isstuck;replace valve.
581B,C